Teenage T-Rexes edge out smaller dinosaur species

WASHINGTON: A team of US scientists has demonstrated that the offspring of huge carnivorous dinosaurs like Tyrannosaurus rex, who grew from the size of house cats to towering monsters, reshaped their ecosystems by outcompeting smaller rival species.

Their study, published in the journal Science on Thursday, helps answer an enduring mystery about the 150-millionyear rule of dinosaurs: why were there many more large species compared to small, which is the opposite of what we see in land animals today?

“Dinosaur communities were like shopping malls on a Saturday afternoon, jam-packed with teenagers,” said Kat Schroeder, a graduate student at the University of New Mexico who led the research.

“They made up a significant portion of the individuals in a species and would have had a very real impact on the resources available in communities.”

Even given the limitations of the fossil record, it’s thought that overall, dinosaurs were not particularly diverse: there are only some 1,500 known species, compared to tens of thousands of modern mammalian and bird species.

What’s more, across the entirety of the Mesozoic era, from 252 to 66 million years ago, there were relatively many more species of large bodied dinosaurs weighing 1,000 kilogrammes (a ton) compared to species weighing less than 60 kilogrammes (130 pounds).

Some scientists put forward the idea that since even the most gigantic dinosaurs begin life as tiny hatchlings, they could be using different resources as they were growing up – occupying the space in ecosystems where smaller species might otherwise flourish.